HOUSTON - Prosperity Bancshares, Inc.® (“Prosperity”) (NYSE: PB), the parent company of Prosperity Bank®, announced the completion of the merger with East Texas Financial Services, Inc. (“ETFS”) and its wholly owned subsidiary First Federal Bank Texas, Tyler, Texas (“Firstbank”), whereby ETFS was merged with and into Prosperity and Firstbank was merged with and into Prosperity Bank effective on January 1, 2013.

ETFS operated four (4) banking offices in the Tyler MSA, including three (3) locations in Tyler, Texas and one (1) location in Gilmer, Texas. As of September 30, 2012, ETFS reported total assets of $191.2 million, total loans of $139.2 million and total deposits of $114.4 million.

Under the terms of the definitive agreement, Prosperity will issue approximately 531,000 shares of Prosperity common stock for all outstanding shares of ETFS capital stock, plus cash in lieu of fractional shares.

Derrell Chapman, Chief Executive Officer of ETFS and Firstbank, will serve as President – Tyler Banking Centers and Micheal Lavender and Joe Hobson will each serve as a Senior Vice President of Prosperity Bank.

David Zalman Chairman and Chief Executive Officer of Prosperity commented, “We are excited to expand our market share in Tyler, the “Rose Capital of the World.” Tyler is a dynamic city in East Texas with higher educational facilities like the University of Texas Tyler and University ofTexas Health System as well as Tyler Junior College. It also has a vibrant medical community and world class hospitals that make it popular with retirees. We look forward to working and growing with Derrell and his team at Firstbank.”

“We are very excited about becoming a part of the Prosperity Bank organization,” said Derrell Chapman, Chief Executive Officer of ETFS and Firstbank. “We believe this merger brings exceptional value to our stockholders, an outstanding level of products and services to our customers and enhanced opportunities for continued growth for our employees.”

Prosperity Bancshares Inc.®, recently named “America’s Best Bank” by Forbes, is a $13.7 billion Houston, Texas based regional financial holding company, formed in 1983. Operating under a community banking philosophy and seeking to develop broad customer relationships based on service and convenience, Prosperity offers a variety of traditional loan and deposit products to its customers, which consist primarily of small and medium sized businesses and consumers. In addition to established banking products, Prosperity offers a complete line of services including: Internet Banking services at http://www.prosperitybanktx.com, Retail Brokerage Services, MasterMoney Debit Cards, 24 hour voice response banking, Trust and Wealth Management and Mobile Banking. Prosperity currently operates two hundred fifteen (215) full service banking locations; fifty-nine (59) in the Houston area; twenty (20) in the South Texas area including Corpus Christi and Victoria; thirty-five (35) in the Dallas/Fort Worth area; twenty-three (23) in the East Texas area; thirty-four (34) in the Central Texas area including Austin and San Antonio; thirty-four (34) in the West Texas area including Lubbock, Midland/Odessa and Abilene; and ten (10) in the Bryan/College Station area.

In connection with the proposed merger of Coppermark Bancshares, Inc. into Prosperity Bancshares, Prosperity Bancshares will file with the Securities and Exchange Commission a registration statement on Form S-4 to register the shares of Prosperity’s common stock to be issued to the shareholders of Coppermark Bancshares, Inc. The registration statement will include a proxy statement/prospectus which will be sent to the shareholders of Coppermark Bancshares, Inc. seeking their approval of the proposed transaction.